Various hydraulically actuated dock levelers have heretofore been provided wherein each leveler has a self-contained pump, associated fittings and a hydraulic piston-cylinder unit for actuating a hingedly mounted deck member or ramp to a predetermined raised position in order to allow the lip, or extension plate, connected to the outer edge of the deck member to be actuated either hydraulically or mechanically to a desired extended position. Where several dock levelers were utilized in a given loading dock installation, the cost of individual levelers of this type became inordinately high because of the need for each leveler to have its own pump and reservoir. Furthermore, the installation and maintenance of these levelers were more difficult and costly. To overcome this problem where multiple hydraulic dock levelers were utilized in a single loading dock installation, the individual pump for each dock leveler was eliminated and in place thereof a single source of pressurized hydraulic fluid was used which was piped so as to serve all of the levelers involved. Representative of such a installation is that disclosed in Artzberger U.S. Pat. No. 4,081,874. While such installations overcame some of the aforenoted problems they were nevertheless beset with one or more of the following shortcomings: (a) the valving system employed restricted the ability of the dock attendants to simultaneously actuate adjoining dock levelers; (b) the hydraulic system was unable to effectively compensate for sudden changes in hydraulic pressure without causing a shut-down of all or substantially all of the levelers associated with the system; (c) the system failed to provide a backup source of pressurized hydraulic fluid; (d) no means was provided for automatically switching from one source of pressurized hydraulic fluid to a second source where alternative sources were available; (e) the hydraulic system could not be readily installed in existing loading dock installations; and (f) the hydraulic system was not readily capable of being utilized in combination with a secondary hydraulic power unit for actuating the lip, hingedly connected to the deck member, in a predetermined timed sequence with the raising of the deck member to a predetermined upwardly inclined position.